This invention relates to forging machines and more particularly to such machines having an adjustable stroke.
For the forging of workpieces having a distinct longitudinal axis, forging machines are employed which are provided with three or more rams equipped with dies, and distributed within a plane, and in particular with four such rams at 90.degree. to one another in an X arrangement. These rams act radially on the workpiece which is guided longitudinally along the system axis. The rams are guided in the machine frame and are constructed at their ends remote from the dies as cylinders of piston-and-cylinder units, or are connected to such units. The piston-and-cylinder units are dimensioned in accordance with the working stroke of the ram in order to minimize the compression volume, this being a major prerequisite for rapid stroke and a defined stroke end position. The stroking position, by which the pass contour produced by the dies is determined, is adjustable by means of crossheads which support the pistons of the piston-and-cylinder units and which are adjustable in the machine frame. A closed pass contour, as is necessary for certain types of work, is obtained through the use of replaceable sets of dies of the appropriate dimensions as in Peter Metzger, "Die numerisch gesteuerte Radial-Umformmaschine und ihr Einsatz im Rahmen einer flexiblen Fertigung" ["The numerically controlled radial forming machine and its employment in flexible manufacturing"], volume 5 of the reports issued by the Institut fur Umformtechnik [Institute of Forming Technology] of the University of Stuttgart, publishers: Springer-Verlag, Berlin - Heidelberg - New York, 1980, pages 36-39, 67-69, 112, 113, 129), or by means of dies which are transversely adjustable at the rams via die holders, said dies featuring mutually overlapping work and side surfaces and being adjusted such that they form a closed pass contour in the relevant stroke end position (European Application No. EP 0 228 030 B1; U.S. Pat. Nos. 4,796,456 and 4,831,864).
In order to achieve a compact design of such forging machines and, at the same time, minimum-clearance ram guidance, the rams according to European Application No. EP 0 228 658 B1 are constructed as pistons or cylinders of piston-and-cylinder units and directly guided, i.e. not offset, in the machine frame. Here -- if double-acting pistons are to be avoided owing to the more complicated seals required -- the pistons or cylinders serving as rams have to be provided with shafts which pass through the complementary cylinders or pistons, and the supporting crossheads which are adjustable in the machine frame, by means of which shafts the piston-and-cylinder units for the ram return strokes operate.